[RV8Squaz]

I know there are a lot of reasons for and against adding aux or long range tanks to the RV's. This is simply another data point for those considering or on the fence about adding them:

I have the standard fuel tanks in the RV-8, 42 gals total. I just got back from San Antonio. I flew non-stop from San Antonio TX to Valdosta GA (804 nm) in 4.1 hrs including an extensive re-route south of the Houston class B. I was flying at 11,000' , 173 KTAS, and winds were from the west at 20 kts for the first half and 35 kts for the second half. My power was set at full throttle (or about 20" MP) and 2550 rpm. Fuel flow was 8.2 gph and ground speeds were anywhere fom 193 kts to 210 kts. I landed with 6 gals. or about 40 mins. of reserve.

I hope this helps anyone considering adding more fuel to the RVs.

Jerry

 

[Mark Burns]

Thanks

Jerry,
That's good information.

Do you have fuel injection?

When running the fuel that low do you run one tank dry and then have the 6 gallons in the other tank? If so, is the preference to use the right tank for the last of the fuel? Seems like that would feed better making left turns in the pattern.

I know 6 gallons is 40 minutes but in the spam cans I rent I'm usually hauling around 30+ gallons for a 1 hour flight! I think 6 gallons would make me a little nervous. (until I got used to it)

Mark

 

[Mel]

Jerry,

When running the fuel that low do you run one tank dry and then have the 6 gallons in the other tank? If so, is the preference to use the right tank for the last of the fuel? Seems like that would feed better making left turns in the pattern.

Mark

If the airplane knows which wing is low, you aren't coordinated.

 

[dan]

If the airplane knows which wing is low, you aren't coordinated.

Thanks, you took the words out of my mouth. But if you're slipping on final with only a handful of gallons left...be careful! Hope you NEED the slip.

 

[pierre smith]

Yeah, and....

How many of you guys have run the airplane dry or very close to it on one tank? Do these airplanes feed just about all of the gas? I've run my -6A down to 3 or 4 gallons in the wings and it never sputtered but I've often wondered.

In the AT-6, I used to alternate from one tank to another every half hour and when the one side ran dry, I'd know how much time remains in the other side. Do any of you guys do this with your RV's?

Thanks,
Pierre

 

[dan]

How many of you guys have run the airplane dry or very close to it on one tank? Do these airplanes feed just about all of the gas? I've run my -6A down to 3 or 4 gallons in the wings and it never sputtered but I've often wondered.

I've run both of my tanks dry on different tests & flights (obviously!). With flop tubes I had 0.3 gal unusable in each tank.

Last time I ran a tank dry was on a long trip with my wife. When the engine sputtered, tears ran down her cheeks. I had told her up and down what was gonna happen, and she knew it was gonna happen, but it still scared the carp out of her. Never again with wifey poo onboard.

 

[Mel]

I ran both my tanks dry (one at a time) during testing. With the standard pick-ups, I found no difference between draining the tanks and running them dry. 19 gallons either way.

 

[RV8Squaz]

Mark,
Yes, I do have fuel injection, a 200 hp IO-360A1A. I ran the right side down to about 1 gal. remaining and the left had 5 gals. The reason I kept more fuel in the left v.s. the right is because my airplane is slightly right wing heavy. The aileron trim is neutral when I have about 5 gals more in the left than the right. The other reason I left more fuel in the left wing is because I don't know what my unuseable fuel in either tank is in a nose low attitude typical of a 1000 fpm descent.
I didn't feel comfortable running the tank completely dry. I am a 7000 hr AF pilot and "shutting down" my only operating engine just doesn't seem like a good idea. I have a VMS 1000C with capacitance senders and a very accurate fuel computer. I have verified the accuracy of both the fuel gages and the fuel computer. I switched tanks when the fuel level went from 2 to 1 and fuel computer indicated 1.3 gals remaining.
I have also verified the unuseable fuel quantity in a level attitude. I did this prior to my first flight by disconnecting the fuel line going to the fuel servo and running the boost pump 'til it quit flowing. I then drained each tank meausuring the quantity I drained. On the right with a standard pickup tube I got 7 oz. On the left with a flop tube I got 13oz. I have a lot of confidence in my fuel system, but I also still rely on my watch.

Jerry

 

[pierre smith]

Thanks...

I ran both my tanks dry (one at a time) during testing. With the standard pick-ups, I found no difference between draining the tanks and running them dry. 19 gallons either way.

I can see doing it once to verify feed factors and so on but I now try to avoid running dry because of the shock cooling on colder days.

Thanks guys,
Pierre

 

[Mark Burns]

I see your point!

If the airplane knows which wing is low, you aren't coordinated.

I hadn't thought of that....DUH!

If you sideslip due to a crosswind with low fuel you had better think hard about it. I guess a crab to very short final would be safer in this instance.

Mark

 

[pierre smith]

Fuel in high wing...

Or just be sure that the wing with the fuel is up! Could starve and quit if it were the low wing and the slip would definitely have the fuel away from the pickup tube

Pierre

 

[Kahuna]

Depends on your bird and mission and your experience.
Flying 4's, I have run many a tank dry cause they have short legs.
On my 8, even with 60 gallons, I run tanks dry all the time. Not a big deal when YOU KNOW YOUR PLANE. I know my range, I know my gages, I know my FF, and as long as everything is agreeing, tank gets run dry and I know exactly when the fan will stop. It is routine for me to take off with 5 gallons in one tank to fly 15 miles to get cheap fuel. Living at an airport with obscene fuel costs sends me flying to get cheap fuel all the time.

After you run a tank dry a dozen times, its no big deal.
Knowing exactly when your tank empties significantly extends the utility of the plane. Always have an out.

I also have on my engine monitor with gps input that tells me fuel data at destination which is an invaluable piece of information. My math airborn is not that good, but the computer is pretty smart. Worst case is airport is closed and I have to divert and land at a nearby airport with only a couple gallons. Twice in my life I have landed, there was no fuel, and I decided to hitch a ride to town for avgas cause I was too low to take off again. Such as life.
Both those times my wife was with me which significantly impacts my launch decision. Both those times I would have launched if I was solo.

 

[gasman]

6oz. remaining

Mark,
Yes, I do have fuel injection, a 200 hp IO-360A1A. On the right with a standard pickup tube I got 7 oz. On the left with a flop tube I got 13oz. I have a lot of confidence in my fuel system, but I also still rely on my watch.
Jerry

I ran mine dry (one at a time) over the airport and had 6oz. left in each tank. As you watch the fuel pressure drop, the motor shut off without a sputter, I switched the fuel selector and DID NOT turn on the electric fuel pump. I started counting and at the count of THREE, the engine fired right up where it left off.... It sure was nice to know this...

Warren

 

[hevansrv7a]

What about the Reg's?

It is routine for me to take off with 5 gallons in one tank to fly 15 miles to get cheap fuel. ...

... Worst case is airport is closed and I have to divert and land at a nearby airport with only a couple gallons. Twice in my life I have landed, there was no fuel, and I decided to hitch a ride to town for avgas cause I was too low to take off again. ...
.. Both those times I would have launched if I was solo.

---------------------------------------------------------------------
​

Federal Aviation Regulation
​

Sec. 91.151

Part 91 GENERAL OPERATING AND FLIGHT RULES​

Subpart B--Flight Rules

Visual Flight Rules​

Sec. 91.151

Fuel requirements for flight in VFR conditions.

(a) No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed--
(1) During the day, to fly after that for at least 30 minutes; or
(2) At night, to fly after that for at least 45 minutes.
...

 

[kentb]

I did it twice during test phase.

How many of you guys have run the airplane dry or very close to it on one tank? Do these airplanes feed just about all of the gas? I've run my -6A down to 3 or 4 gallons in the wings and it never sputtered but I've often wondered.

In the AT-6, I used to alternate from one tank to another every half hour and when the one side ran dry, I'd know how much time remains in the other side. Do any of you guys do this with your RV's?

Thanks,
Pierre

Once on each tank, just so that I could get an accurate usable quantity for each tank. I measured 18.2 and 18.3 gal to when they quit in cruse flight. Both time the other tank was almost full and I was at altitude over some airports.
I had never done this before while flying spam cans, so it was kind of exciting for about 5 seconds. When it started sputtering I just flipped the selector and reached over and flipped on the fuel pump. By the time the fuel pump starts up the engine is running smooth.

The last time that I ran it dry, I was trying to run it low with the intent of draining the last couple of gal out in the hangar. I was only at about 1500 ft agl heading back to the airport (10 miles away) and it started sputtering when I didn't expect it.
I quickly selected my other tank and turned the fuel pump on, but this time the sputtering continued for along time (10 seconds maybe). I was busy looking for the best off airport field when it finally smoothed out. I checked the altitude and had not lost any the speed was down maybe 5 knots and during the sputtering the rpm may have gone down 200.

I don't think that running the fuel out of one tank while flying is a big deal, if your are expecting and ready for it. As Dan said I would never do it with TWOB (the wife on board).

I think that my extended range strategy would be to use 4 gal from each tank. The last switch would leave 2 gal in the first tank and then I would land before I used more then 2 gal out of the second tank. I would be landing with 4 gal in second tank and 2 in the first tank.

Kent

 

[Ron Lee]

Empty tanks

I have run tanks dry on purpose about six times...twice with others flying so they could experience it. The first time I was circling a little used runway and as the fuel got closer and closer to empty the radius of my circle got smaller and smaller. To this day I don't understand the aerodynamics of that process.

 

[Nuisance]

I know there are a lot of reasons for and against adding aux or long range tanks to the RV's. This is simply another data point for those considering or on the fence about adding them:

I have the standard fuel tanks in the RV-8, 42 gals total. I just got back from San Antonio. I flew non-stop from San Antonio TX to Valdosta GA (804 nm) in 4.1 hrs including an extensive re-route south of the Houston class B. I was flying at 11,000' , 173 KTAS, and winds were from the west at 20 kts for the first half and 35 kts for the second half. My power was set at full throttle (or about 20" MP) and 2550 rpm. Fuel flow was 8.2 gph and ground speeds were anywhere fom 193 kts to 210 kts. I landed with 6 gals. or about 40 mins. of reserve.

I hope this helps anyone considering adding more fuel to the RVs.

Jerry

Yah, good thing you were going east, or you would be taking your wings apart

 

[RV8Squaz]

Yah, good thing you were going east, or you would be taking your wings apart

Yeah, I know I wouldn't have gotten as far but my butt doesn't know the difference. After 4 hrs my butt was more than ready to get out of the plane!

 

[dan]

Yeah, I know I wouldn't have gotten as far but my butt doesn't know the difference. After 4 hrs my butt was more than ready to get out of the plane!

High quality seat cushions sure go a long way to extending your virtual range. The only reason I get out of the plane on long trips these days is to top off. If I didn't have to stop for fuel I wouldn't stop. Got O2, got piddle packs (or Gatorade bottles), and good seat cushions (Classic Aero). Comfy.

 

[RV8Squaz]

High quality seat cushions sure go a long way to extending your virtual range. The only reason I get out of the plane on long trips these days is to top off. If I didn't have to stop for fuel I wouldn't stop. Got O2, got piddle packs (or Gatorade bottles), and good seat cushions (Classic Aero). Comfy.

Nope my seat cushion is very comfy. Many people have given me positive feedback on it and the lumbar. The fact is I have a 2, maybe 2 1/2 hr butt. The 4 hrs was 1 1/2 hrs past my butt limit. Besides getting out more frequently allows me to explore new airports and meet some more friendly airport people.

 

[Bob Axsom]

I have run them dry

I have 4 tanks totaling 55 gallons and my fuel burn rate is approximately 10 gallons per hour (O-360-A1A). The tip tanks hold 9.5 gallons each and I use a half hour per tank switch interval at the start. On the first cycle I takeoff on a main, after 0.5 hr. switch to opposite tip, then to the other tip, then the remaining main. The second cycle is where it gets interesting. I go back to a tip and monitor the fuel pressure for 0.3 hr. or a steady drop in fuel pressure whichever comes first and switch to the other tip. I find that 0.8 hr. is the most I can reliably get out of the 9.5 gallon tip tanks. After the tip tanks I continue half hour cycles with the mains. I have never ran them dry yet but the red light will be on for these tanks before I hit 1.5 hours. I have good EI gauges for all four tanks but the float senders don't float for a while during the calibration fills so there is considerable pad in the alarm. Before I incorporated the fuel pressure in my margin management I ran the tanks dry thinking I still had a little time in the tank. It requires a little time for the engine to restart and my second action after the tank switch is to turn on the Aux. fuel pump.

Bob Axsom

 

[kentb]

Bob, when you run your tanks low...

What is it your looking for in the fuel pressure?
Can you see a change in pressure before the engine starts running rough?

Kent

 

[RVbySDI]

. . .but it still scared the carp out of her. Never again with wifey poo onboard.

Carp! Do those things swim out when they are scared or do they come flying out?

 

[dan]

Carp! Do those things swim out when they are scared or do they come flying out?

Well, all I know is...when a carp takes a **** the VAF auto-editor cuts all sorts of bull**** out of each ****in post.

 

[GrayHawk]

Well, all I know is...when a carp takes a **** the VAF auto-editor cuts all sorts of bull**** out of each ****in post.

It's not just individual words or 4 letters at the beginning or end, but the right 4 letters within a perfectly valid word.....
Such as: the carp was swimming up the Wa****a river.

 

[Captain Avgas]

On the first cycle I takeoff on a main, after 0.5 hr. switch to opposite tip, then to the other tip, then the remaining main.
Bob Axsom

Bob, how does your aux fuel feed system work. I presume that you may not be feeding from the tips into the mains. Obviously to feed from the tip into the main you must first use some fuel from the main on the same side.

By the way where did your tip tanks come from.

 

[RVbySDI]

It's not just individual words or 4 letters at the beginning or end, but the right 4 letters within a perfectly valid word.....
Such as: the carp was swimming up the Wa****a river.

Hey, you know I live just a few miles from the Wa****a river. I am sure there are quite a few carp swimming in that river. You are right. I could not even spell out the Wa****a river without it putting **** 's where the offensive letters were. Interesting.